in tutorial, you abserved the following three experiments involving a student si
ID: 2242227 • Letter: I
Question
in tutorial, you abserved the following three experiments involving a student sitting at rest on a stool, holding a spinning bicycle wheel as shown. (diagram)
Ex 1. the student places his arm against the side of the wheel, slowing it to half its initial angular speed.
ex 2. the student places his arm against the sideof the wheel, bringing it to a stop.
ex 3. the student quickly flips the wheel over (so that it is spinning clockwise when viewed from above, with the same angular speed it had initially)
Q 1. - you observed that the final angular speed of the student in experiment 3 is greater than that in experiment 2. account for this result using the ideas developed in the tutorial.
Q 2. - rank the experiments according to the final kinetic energy of the wheel, from largest to smallest. ifthe final kinetic energy of the wheel is the same in any two experiments, state so. (explain)
Q3 . -rank the experiments according to final kinetic energy of the student, from largest to smallest. if the final kinetic energy of the student is the same in any two experiments state so. (explain)
Q4. -rank the following four quantities from largest to smallest: the initial kinetic energy of the wheel (k_wi) and the final kinetic energy of the student wheel system in experiments 1,2, 3. explain.
Explanation / Answer
In experiment 1, The system is a closed one and the final angular momentum is half of initial. Therefore, student aquires an angular momentum of L/2 in order to conserve the total angular momentum L. Now the kinetic enegry of the student is (L/2)^2/(2*I)
Q1 - In exp 2, some of the energy is lost due to friction when student places his arm against the sideof the wheel. In exp 3, the student does work to flip the angular momentum and gains some energy in the process.
Q2- Not sure about this one, but in first experiemnt the wheel comes to half of its original momentum, so K.e will also reduce by half, in exp 2, wheel comes to a stop, so K.E is zero,, In experiment three the direction is reversed but K.E will be same.
Q3 - Energy in exp 1 = (L/2)2 / 2I = 2IL2 / 4 = L2 / 8I
Energy in exp 2 = 1/2 * L2*I = L2 / 2I
Energy in exp 3 = 2L2 / I
SO, Kinetic energy ranking is 3 > 2 > 1 ( LARGEST IS 3 AND SMALLEST IS 1)
Q4 - Initial kinetic energy of wheel is same is all experiements
Final kinetic energy of student wheel system = 3 > 1 > 2
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